The present invention relates generally to exercise machines and, in a preferred embodiment thereof, more particularly provides a leg extension exercise machine having improved leg length and exercise motion range adjustment mechanisms incorporated therein to facilitate the operation of the machine by exercisers utilizing rehabilitative leg exercise programs.
Leg extension exercise machines are well known in the exercise machine art and typically comprise a seat structure carried by a support frame to which is pivotllly mounted a leg force input lever. Via a sprocket, chain and cam linking system, the force input lever is operatively connected to a multi-element weight stack carried by the support frame, a selectively variable portion of the weight stack being operatively connectable to an outer end of the linking system to yieldingly resist leg-driven pivotal motion of the input member.
To use such a machine, the exerciser sits in the machine seat, with his legs extending downwardly over the front edge thereof, and hooks his feet under padded foot engagement members secured to the outer end of the force input lever. By extending his legs toward their straightened positions, the lever is pivoted against the resistive force of the selected portion of the weight stack as it is lifted from the balance of the weight stack. When the legs have been extended to a desired degree, they are slowly lowered against the pivotal resistance of the weight stack portion as it is lowered to its start position.
While leg exercise machines of this general type are widely used and are quite beneficial to able bodied exercisers, their use has, in the past, has been somewhat limited as to exercisers attempting to use the machines for rehabilitative exercise purposes following, for example, knee or leg surgery. In such instances of rehabilitative machine use, the exerciser is typically limited to relatively low resistive weight loads and/or is further limited as to the angular range through which he may safely move the force input lever against the resistance of the predetermined portion of the weight stack. For example, the exerciser using the machine in a rehabilitative leg exercise routine may only be permitted to subject his legs to pivotal weight resistance within a small portion of the overall available pivotal range of the force input member.
Various proposals have been made to accommodate leg extension exercise machines of this general type to limited rehabilitative use thereof. For example, various mechanisms have been proposed to selectively limit the weight-resisted angular range of the force input lever. However, conventional approaches to this angular limitation have typically necessitated either an undesirable variance in the angular relationship between the input lever and the machine cam, or required that the input lever be pivoted against the resistance of the weight stack to effect such angular range adjustment.
Another problem associated with attempts to utilize machines of this type in limited, rehabilitative leg exercise programs is associated with the height adjustment of the foot engagement structure carried by the force input lever. Specifically, to adjust the actual foot engagement portion of such structure to accommodate exerciser leg length variances, the center of gravity of the foot engagement structure has heretofore been unavoidably shifted, thereby disturbing the rotational balance of the input lever provided by its associated counterweight. Particularly when the exerciser in a rehabilitative exercise program is limited to using a very small portion of the weight stack, this shifting of the foot engagement structure center of gravity significantly alters the leg force required to pivot the lever for varying leg lengths. At the very low weight resistance levels involved in such rehabilitative exercise program this is a decidedly undesirably result.
From the foregoing it can readily be seen that improvements are needed in leg exercise machines of this general type in order to better facilitate their use in rehabilitative leg exercise programs. It is accordingly an object of the present invention to provide a leg extension exercise machine in which such improvements are advantageously incorporated.